Related Applications
The present application relates to subject matter similar to that disclosed in U.S. patent application Ser. No. 462,798, filed Jan. 10, 1990 by the applicants herein.
The present invention relates to a measuring device for contactless control of a design of metallic screwshaped structural elements.
Measuring devices of the above mentioned general type are known in the art. In the known measuring device the design of screws is determined with the use of coils through which high frequency alternating current flows. The measuring principle deals with the change of the impedance of the coils, when the shape of the structural element varies. The coils cover integrally, over the whole length or over a partial region, the distance between the coils and the structural element. Thus, there is a possibility that the different screw errors cause an opposition action during generation of the eddy current. Thereby, both measuring signals are compensated, and the measuring device releases a measuring signal for a proper screw, despite the defective shape of the screw. This would be the case when the screw to be measured has too great a thread diameter and too short a thread length, or when the thread has too narrow a pitch and simultaneously has too small an outer thread diameter.